Boom extension means

ABSTRACT

In a boom consisting of more than three boom members telescopically extensibly connected with each other and including a plurality of hydraulic cylinders each having compressed oil chambers on the extending and retracting sides thereof and arranged to extend between adjacent boom members, a boom extension means comprising oil supply and discharge lines connected to an oil pressure source; oil pressure supply and discharge lines connecting said plurality of hydraulic cylinders with each other; a plurality of control valve means each connected to each of the secondly mentioned oil pressure supply and discharge lines which are connected between adjacent hydraulic cylinders, each of said control valve means being so adapted as to be normally maintained in a closed position to permit the flow of oil pressure in the same direction and forcibly biased into an opened position only when the hydraulic cylinder relating to said control valve is operated to an utmost limit of extension or retraction, thereby permitting the flow of oil pressure in a direction opposite to said same direction, the opening and closing operations of said control valve being automatically effected in association with movement of the hydraulic cylinder relating to said control valve.

I United States Patent 11 1 1111 3, I Ohniwa et al. May 7, 1974 BOOMEXTENSION MEANS [57] ABSTRACT [75] Inventors: Kazuhiro Ohniwa; SeutiIshikawa,

both of Takam t Japan In a boom consisting of more than three boommembers telescopically extensibly connected with each [73] Asslgnee s z'l Tekkosho other and including a plurality of hydraulic cylinders aamatsu apan each having compressed oil chambers on the extend- [22]Filed; Jan. 18, 1972 ing and retracting sides thereof and arranged toextend between adjacent boom members, a boom exten- [21] Appl 218822sion means comprising oil supply and discharge lines Related US,Application D t connected to an oil pressure source; oil pressure sup-[63] continuation of Sen 11,131, Feb. 13 1970' ply and discharge linesconnecting said plurality of hyabandoned. draulic cylinders with eachother; a plurality of control valve means each connected to each of thesecondly 52 us. c1. 212/55, 52/115, 91/411 R, mentioned Oil Pressure ppy and discharge lines 92/14 which are connected between adjacenthydraulic cyl- [5l] Int. Cl. Fl5b 15/16 indersr' each of Said controlValve means being so 53 Fie|d f Search 55 35, 91/167 R adapted as to benormally maintained in a closed posi- 91/168. 411 R. 4114; 52/115-118;92/146; 110" to permit the flow 01011 pressure in the same di- 6Q/97 Hrection and forcibly biased into an opened position only when thehydraulic cylinder relating to mid con- 5 References m trol valve isoperated to an utmost limit oi extension UNITED STATES PATENTS orretraction, thereby permitting the flow of oil pressure in a directionopposite to said same direction, the 823i: 3 3 opening and closingoperations of said control valve Primary Examiner- -Evon C. BlunkAssistant Examiner.lohnny D. Cherry Attorney, Agent, or Firm-Shlesinger,Fitzsimmons & Shlesinger being automatically effected in associationwith movement of the hydraulic cylinder relating to said control valve.

5 Claims, 7 Drawing Figures PATENTEDIH 7 1914 SHEEI 2 [IF 7 TV a N rm nwei PATENTEDMY mm $809,248

SHEEI 3 (1F 7 INVENTOR K h Ohniwaand.

Sean lshk'lrayw ATTORNEY5 PATENTEDIAY 71914 I also-SL248 sum 5 or 7 5161 Q1 86 c B 75 72 61 71 BYMM/FJ -JM 12k ATTORNEYS BOOM EXTENSION MEANSThis is a continuation of application Ser. No. 1 1,131, filed Feb. 13,1970, now abandoned.

The present invention relates to an extension means of a boom consistingof at least three extensible boom members telescopically fitted to eachother.

The most commonly used extension means of a boom consisting of at leastthree extensible boom members and operated by hydraulic cylinders is soconstructed that the hydraulic cylinders are respectively disposed toextend between two adjacent boom members and oil supply lines aredisposed in the respective hydraulic cylinders so as to cause these boommembers to extend and retract by the working pressure suppliedtherefrom. The conventional and existing arrangements of the oilpressure supply lines or circuits in the multistage boom extensiblemeans of this type are various: one of them is such that oil pressuresupply circuits are respectively arranged at respective hydrauliccylinders of respective boom members, and a valve is connected to eachof oil pressure supply lines, thereby to independently control theextending and retracting operations of respective boom members; and theother practice is such that a pair of oil pressure supply and dischargelines or circuits are arranged for respectively connecting thecompressed oil chamber on the extending side and the compressed oilchamber on the retracting side of each hydraulic cylinder connectedbetween boom members and a valve is connected therebetween for switchingthe hydraulic pressure. In the latter case, as a means for regulatingthe operational sequence of respective boom members, such ways have beenselectively or in combination used as connecting adjacent 7 boom membersby cables so as to operate each of them in regular sequence; ordisposing between adjacent boom members any suitable securing meansautomatically engaging or disengaging in association with the extendingmotion of each boom; or making a dimensional difference in the areas onpiston rods on which the working pressure is exerted in the directionsof extending and retracting pistons of respective hydraulic cylinders.

These conventional boom extension means as described, however,respectively present many disadvantages and inconveniences in viewpointsof structure and operation that to connect a valve for switching thehydraulic pressure to every hydraulic cylinder connected between boommembers is not only difficult in piping work but also inconvenient inoperating each valve; to use cables or securing means for controllingthe operational sequence of respective boom members results incomplexity in structure of relevant portions; and to control theoperational sequence of boom members by making a dimensional differencein the pressure exerted areas on respective piston rods results inunnecessary enlargement of a boom, because, with increment in numbers ofboom members, the working pressure exerted area on the piston rod of thepreceding hydraulic cylinder of which the diameter is smaller than thatof succeeding cylinder must be larger than that on the piston rod of thesucceeding hydraulic cylinder of which the diameter is larger than thatof preceding cylinder. This requirement issatisfied by impartingsufficient strength to the preceding cylinder. However, this inevitablyresults in an unnecessary increase in size and strength of thesucceeding hydraulic cylinder.

The present invention overcomes these drawbacks as described.Accordingly, an object of the present invention is to provide anextension means of a multi-stage boom in which the oil pressure issupplied to and discharged from all of the hydraulic cylinders foroperating the respective boom members, through oil pressure supply anddischarge lines to each of which a valve for switching the hydraulicpressure is connected, and operation of the respective hydrauliccylinders for retracting and extending the boom members is automaticallyregulated in relation with the operational positions of preceding andsucceeding hydraulic cylinders, thereby assuring the regular operationalsequence of respective boom members by a simple operation.

In a boom consisting of more than three boom members telescopicallyextensibly connected with each other and including a plurality ofhydraulic cylinders each having compressed oil chambers on extending andretracting sides and arranged between adjacent boom members, the boomextension means comprises oil supply and discharge lines connecting toan oil pressure source; oil pressure supply and discharge linesconnecting said plurality of hydraulic cylinders with each other;

a plurality of control valve means each connected to each of secondlymentioned oil pressure supply and discharge lines connected betweenadjacent hydraulic cylinders, each of said control valve means being soadapted as to be normally maintained in a closed position to permit theflow of oil pressure in the same direc tion and forcibly biased into anopened position only when the hydraulic cylinder relating to saidcontrol valveis operated to an utmost limit of extension or retraction,thereby permitting the flow of oil pressure in a direction opposite tosaid same direction, open and close operations of said control valvebeing automatically effected in association with movement of thehydraulic cylinder relating to said control valve.

A boom extension means is characterized in that one of oil pressuresupply and discharge lines connected to an oil pressure source isdirectly connected to the compressed oil chamber on the retracting sideof the first hydraulic cylinder most adjacent to a base portion of theboom; said one of oil pressure supply and discharge lines being furtherconnected to the compressed oil chambers on the retractingsides of thehydraulic cylinders located in succeeding positions with respect to saidfirst hydraulic cylinder through oil pressure supply and discharge linesconnecting adjacent hydraulic cylinders and each having a control valve,said control valves being so adapted as to be normally maintained inclosed position to prevent the flow of oil pressure in a dischargingdirection from the compressed oil chamber on the retracting side of thehydraulic cylinder located in the succeeding position with respect tosaid control valve to that of the preceding hydraulic cylinder whilepermitting the flow of oil pressure in a direction opposite thereto, andforcibly biased into an opened position only when said precedinghydraulic cylinder is moved into an utmostly extended position, therebypermitting the flow of oil pressure in said direction of dischargingfrom the succeeding compressed oil chamber on the retracting side, andthe other of oil pressure supply and discharge lines is directlyconnected to the compressed oil chamber on the extending side of thehydraulic cylinder most adjacent to a top end portion of the boom, saidother of oil pressure supply and discharge lines being further connectedto the compressed oil chambrs on the extending sides of hydrauliccylinders preceding said hydraulic cylinder most adjacent to the topportion of the boom through oil pressure supply and discharge linesconnected between adjacent hydraulic cylinders and each having a controlvalve, said control valves being so adapted as to be normally maintainedin closed position to prevent the flow of oil pressure in thedischarging direction from the compressed oil chamber on the extendingside of the hydraulic cylinder located in a preceding position withrespect to said control valve to the compressed oil chamber on theextending side of the succeeding hydraulic cylinder while permittingflow of oil pressure in an opposite direction thereof and forciblybiased into an opened position only when said succeeding hydrauliccylinder is moved into an utmost retracted position, thereby permittingthe flow of oil pressure to the compressed oil chamber on the extendingside of said succeeding hydraulic cylinder from the preceding compressedoil chamber; opening and closin g operations of said control valve beingautomatically effected in association with the retracting movement ofcorresponding hydraulic cylinder.

And, said boom extension means is further characterized in that one ofoil pressure and discharge lines is directly connected to the'compressedoil chamber on the extending side of the first hydraulic cylinder mostadjacent to the base porition of the boom; said one of oil pressuresupply and discharge lines being further connected to the compressed oilchambers on the extending sides of hydraulic cylinders located in thesucceeding positions with respect to said first hydraulic cylinderthrough oil supply and discharge lines each having a control valve, saidcontrol valves being so adapted as to be normally maintained in closedpositions to prevent the flow of oil pressure in the direction of oilsupply from the compressed oil chamber on the extending side of thehydraulic cylinder located in a preceding position with respect to saidcontrol valve to that of the succeeding hydraulic cylinder whilepermitting flow of oil pressure in the opposite direction thereto, andforcibly biased to an opened position when said preceding hydrauliccylinder is extended to the extremity, thereby permitting the supply ofoil pressure to the compressed oil chamber on the-extending side of thesucceeding hydraulic cylinder, the opening and closing operations ofsaid control valve being automatically effected in association withmovement of the hydraulic cylinder relating to said control valve; andthe other of said oil pressure supply and discharge lines is directlyconnected to the compressed oil chamber on the retracting side of thehydraulic cylinder most adjacent to the top end portion of the boom;said other of oil pressure supply and discharge lines being furtherconnected to respective compressed oil chambers on the retracting sidesof hydraulic cylinders located in the preceding position with respect tosaid hydraulic cylinder most adjacent to the top portion of the boomthrough oil pressure supply and discharge lines each having a controlvalve, said control valves being so adapted as to be normally maintainedinclosed positions to prevent the flow of oil pressure in the directionfrom the compressed oil chamber on the retracting side of the hydrauliccylinder located in the succeeding position with respect to said controlvalve to that of the preceding hydraulic cylinder while permitting flowof oil pressure in the opposite direction thereto, and forcibly biasedinto an opened position only when said succeeding hydraulic cylinderbecomes extended to the extremity, thereby permitting the oil flow tothe compressed oil chamber on the retracting side of the precedinghydraulic cylinder, the opening and closing position of said controlvalve being automatically effected in association with movement of thehydraulic cylinders relating to said valve.

The accompanying drawings show two embodiments of the present invention,wherein,

FIG. 1 is a longitudinal sectional side view of a boom consisting offour boom members, partly broken away,

FIG. 2 is a longitudinal sectional view of respective hydrauliccylinders, partly broken away,

FIG. 3 is a longitudinal sectional view illustrating the respectivemechanical check valves,

FIG. 4 is a hydraulic diagram showing the pipe lines for supplying anddischarging oil to and from the different boom cylinders and showingalso the different of control valves of the system,

FIG. 5 is a longitudinal sectional side view a of fourstage boom builtaccording to another embodiment, part being broken away,

FIG. 6 is a longitudinal sectional view of different hydraulic cylindersof this boom, and FIG. 7 is a longitudinal sectional view illustratingmechanical check valves for this boom.

For explanatory convenience and better understanding of this invention,the boom extension means which is used with a boom consisting of fourboom members is explained throughout the examples.

In FIGS. 1 through 3 showing the first embodiment, numerals l, 2, 3 and4 are first, second, third and fourth cylindrical boom members,respectively, which are telescopically and slidably fitted one withinanother. These cylindrical boom members are similar in construction withthe exception that the third boom member 3 is internally divided by alongitudinally extending partitioning wall 3a into an upper space and alower space. Numeral 11 is a first hydraulic cylinder arranged withinthe first and second boom members 1, 2 to extend into the upper space ofthe third boom member 3 and having a cylinder portion 11a of which thebase portion is connected by a pivot 22 to the base portion of thesecond boom member 2 and a piston rod 11b longitudinally extendingtherethrough and connected at one end to the base portion of the firstboom member 1 by a pivot 21.

Numeral 12 is a second hydraulic cylinder longitudinally arrangedbetween the second and third boom members and having a cylinder portion12a pivotally connected at its base portion by pivot 24 to the baseportion of the third boom member 3 and a longitudinally extending pistonrod 12b pivotally connected at 23 at its one end to the base portion ofthe second boom member 2.

Numeral 13 is a third hydraulic cylinder longitudinally arranged betweenthe third and fourth boom members 3, 4 and having a cylinder portion 13aconnected at its top portion to the top portion of the fourth boommember 4 by a pivot 26 and a longitudinally extending piston rod 13bconnected at its one end to the base portion of the third boom member 3by a pivot 25.

Numeral 27 is a roller for carrying the top end of the first hydrauliccylinder 1 1 and numeral 28 is a roller for carrying the top end of thesecond hydraulic cylinder 12.

The arrangement of the oil pressure supply lines or circuits to therespective hydraulic cylinders l l, 12, 13 will be described. Numeral 29is anoil pressure supply line connected to a port 30 formed at the baseportion of the piston rod 13b of the third hydraulic cylinder 13 andcommunicating with a compressed oil chamber 130 in said hydrauliccylinder 13. Numeral 31 is an oil pressure supply line connected to aport 32 formed on the base portion of the piston rod 11b of the firsthydraulic cylinder 1 l and communicating with a chamber 11d in saidhydraulic cylinder. Numeral 33 is a valve for switching the direction offlow of oil pressure to the oil pressure supply lines 29, 31. Said oilpressure supply line 29 connected to the port 30 moving with the thirdboom member 3 at the time of extending and retracting operations of theboom member is a flexible hose and sufficiently long to extend accordingto necessity, and being shortened by any suitable means, for example, apulley (not shown) connected thereto.

Said port 30 communicates with a chamber 130 in the third hydrauliccylinder 13 through a hollow piston rod 13b while the port 32communicates with a chamber 11d inthe first hydraulic cylinder 11through a pipe 34. The chambers 11c, 12c in the first and secondhydraulic cylinders 11, 12 and the chambers 12d and 13d in the secondand third hydraulic cylinders 12, 13 are respectively connected to oilchamber 13c when the boom is being extended and to the chamber 11d whenthe boom is being retracted, namely, to the oil supply lines 29, 31,respectively, under these conditions In detail, the compressed oilchamber 11c on the extending side of the first hydraulic cylinder 11 isconnected to the compressed oil chamber 12c on the extending side of thesecond hydraulic cylinder 12 through a port 35, an oil pressure supplyline 36 with a mechanical check valve D connected thereto, a port 37 andhollow piston rod 12b, said compressed oil chamber 120 on the extendingside of the second hydraulic cylinderl2 being further connected, througha port 38 and an oil pressure supply line 39 with a mechanical checkvalve C, to the port 30 to which is connected the oil pressure supplyline 29 communicating with the compressed oil chamber 130 on theextending side of the third hydraulic cylinder 13. The compressed oilchamber 13d on the retracting side of the third hydraulic cylinder 13 isconnected to the compressed oil chamber 12d on the retracting side ofthe second hydraulic cylinder 12 through a pipe 49, a port 40, an oilsupply line 41 with a mechanical check valve B and a port 42, saidcompressed oil chamber 12d on the retracting side of the secondhydraulic cylinder 12 being further connected to the compressed oilchamber 11d on the retracting side of the 'first hydraulic cylinder 11through a pipe 43, a port 44, an oil pressure supply line 45 with amechanical check valve A and a port 46.

Said mechanical check valve A is secured to the second boom member 2 asbest seen in FIG. 3, said mechanical check valve having a valve rod Abnormally maintained in a closed position to prevent the flow of oil inthe discharging direction from the compressed oil chamber 12d on theretracting side of the second hy-,

draulic cylinder 12 to the compressed oil chamber 11d on the retractingside of the first hydraulic cylinder 11 but to permit the supply of oilpressure only in the opposite direction thereto. Said mechanical checkvalve A is so adapted that, as soon as the first hydraulic cylinder 11is extended to move thesecond boom member 2 into the utmost extendedposition, its valve rod Ab normally urged to the closed position isforcibly biased to open position by an engaging projection 47 providedon an internal periphery of the first boom member 1. It is automaticallyreturned to and maintained in the closed position to control the fiow ofoil in the discharging direction from the compressed oil chamber 12d onthe retracting side of the second hydraulic cylinder 12 to thecompressed oil chamber 11d on the retracting side of the first hydrauliccylinder 1 1 while permitting oil to flow in the opposite direction,when said hydraulic cylinder 11 and the second boom member 2 are in theother extending and retracting positions. The mechanical check valve Bsecured to the third boom member 3 is the same as the valve A both inits operation and structure. As soon as the second hydraulic cylinder 12is operated to the extremity of extension,

namely, the third boom member 3 is extended to the extremity, the valverod Bb of the valve Ba normally urged to the closed position is broughtinto engagement with projection 48 provided on an internal periphery ofthe second boom member 2, thereby to be forced to a biased or openedposition. Said valve rod Bb is automatically returned to normally closedposition to prevent the flow of oil in the discharging direction to thecompressed oil chamber 12d on the retracting side of the secondhydraulic cylinder 12 from the compressed oil chamber 13d on theretracting side of the third hydraulic cylinder 13 but permitting thesupply of oil only in the opposite direction, when the second hydrauliccylinder 12 is in the other extending and retracting positions.Operation of the mechanical check valve C is such that when the thirdhydraulic cylinder 13 is operated to the extremity of retraction,namely, the fourth boom member 4 is retracted to the extremity, thevalve rod Cb of the valve C, which is normally urged to closed position,is forced by the base portion of the fourth boom member 4 into a biasedor opened position; and it is automatically returned to normal closedposition to prevent flow of oil in the discharging direction fromchamber 12c to chamber 136 while permitting supply of oil only in theopposite direction when said third hydraulic cylinder 13 is in the otherretracting and extending positions. The mechanical check valve D is soadapted that, when the second hydraulic cylinder 12 is operated to theextremity of retraction, namely, the third boom member 3 is retracted tothe extremity, the valve rod Db normally urged to the closed position isforced by the base portion of the third boom member 3 into a biased oropened position. It is automatically returned to the normal closedposition to prevent the flow of oil in the discharging direction fromthe compressed oil chamber on the extending side of the first hydrauliccylinder 11 to the compressed oil chamber on the extending side of thesecond hydraulic cylinder 12 but to permit the supply of oil only in theopposite direction. The boom extension means is operated as follows.

When the respective hydraulic cylinders 11, 12, 13 are put in theretracted position as shown in FIG. 2 and if the valve 33 is operated toconnect the oil pressure supply line 29 to the pressure line and connectthe oil supply line 31 to the tank line, the oil pressure simultaneouslyacts on respective compressed oil chambers 11c, 12c, on the extendingsides of respective hydraulic cylinders 11, 12, 13 in the direction toextend these hydraulic cylinders, since the mechanical check valves Cand D constantly permit the flow of oil pressure in the direction of oilpressure supply. In this situation, the discharge of oil from chambers12d, 13d on the retracting sides of the second and third hydrauliccylinders 12, 13 is prevented by the mechanical check valves A and B,hence passage of oil through the lines 45 and 41 in the dischargingdirection is also prevented. While discharge from the compressed oilchamber 11d on the retracting side of the first hydraulic cylinder 11 ispermitted at this time, only the first hydraulic cylinder 11, namely,the second boom member 2, is caused to extend. And, when the second boommember 2 is moved by the first hydraulic cylinder 11 to the extremity ofextension, the mechanical check valve A is forcibly biased by theengaging projection 47 to permit oil discharge from chamber 12d of thesecond hydraulic cylinder 12 through chamber 11d, whereby the secondhydraulic cylinder 12 is operated to cause extending motion of the thirdboom member 3. When the third boom member 3 is extended to theextremity, the mechanical check valve B is forcibly biased to permit thedischarge of oil from chamber 13d through chamber 12d, whereby the thirdhydraulic cylinder 13 is caused to extend, thereby to move the fourthboom member 4 into the extended position.

If the valve 33 is switched to the other direction to connect the oilpressure supply 31 to the pressure line and the line 29 to the tank linewhen all of the boom members are in the extended positions, the oilpressure acts on the compressed oil chambers 11d, 12d, 13d in thedirection of retract these cylinders, since the mechanical check valvesA and B normally permit passage of the oil pressure in the feeddirection. In the situation where all boom members arein the extendedposition, the discharge of oil from the compressed oil chambers 12c, lieon the extending side of the second and first hydraulic cylinders 12, 11is prevented by the mechanical check valves C and D, while the dischargefrom chamber 13c is only permitted; hence the third hydraulic cylinder13 is retracted, thereby moving the fourth boom member .4 to theretracting position. When the fourth boom member 4 is retracted to itsextremity by operation of the third hydraulic cylinder 13, themechanical check valve'C is forcibly biased by the base portion of thefourth boom member 4 to permit the oil discharge from the compressed oilchamber 120 on the retracting side of the second hydraulic cylinder. 12through the chamber 130 on the extending side of the third hydrauliccylinder 13, whereby the second hydraulic cylinder 12 is retracted tocause retraction of the third boom member 3. When the third hydrauliccylinder 13 is retracted to move the fourth boom member 4 into itsutmost retracted position, the mechanical check valve C is forciblybiased by the base portion of the fourth boom member 4 to permit the oildischarge from chamber 120 through chamber 13,whereby the secondhydraulic cylinder 12 is retracted to cause re traction of the thirdboom member 3. When the second hydraulic cylinder 12 is fully retractedto move the third boom member 3 into its fully retracted position, themechanical check valve D is forcibly biased to permit the oil dischargefrom chamber 11c, whereby the first hydraulic cylinder 11 is retractedto move the second boom member 2 to the retracted position.

The example is shown in which the mechanical check valves A, B, C and Dare respectively connected to the oil discharge lines 45, 41 connectedto the chambers 12d, 13d on the retracting sides of the second and thirdhydraulic cylinders and connected to the oil discharge lines 39, 36connected to the compressed oil chambers 12c, 110 on the extending sidesof the second and first hydraulic cylinders 12, 11. The control valvesto be connected to these pipe lines 45, 41, 39 and 36 are not limited tothe check valves having a structure as described in the foregoing, butmay be such valves A, B, C and D as are automatically opened and closedaccording to the extending and retracting operations of respectivehydraulic cylinders 11, 12, 13, like the mechanical check valves-A, B, Cand D as described. The arrangement of the oil pressure supply lines inand between respective hydraulic cylinders to which valves A, B, C and Dare respectively connected is diagramatically shown in FIG. 4. So far asthese valves A, B, C and D in this example are so constructed that thevalve A is caused to open only when the hydraulic cylinder 11 is in theextremity of expansion; the valve B is opened only when the secondhydraulic cylinder 12 is extended to the extremity; the valve C isopened only at the extremely retracted position of the hydrauliccylinder 13; and the valve D is opened only at the extremely retractedposition of the hydraulic cylinder 12, the respective boom members canbe automatically controlled to move in regular sequence, like the foregoing embodiment described. i

A further embodiment is shown which is substantially similar to thefirst embodiment in it construction.

In FIGS. 5 through 7, numerals S1, 52, 53 and 54 are first, second,third and fourth cylindrical boom members telescopically slidablyconnected to each other and having the same structure with the exceptionthat the third boom member 53 is internally divided by a longitudinallyextending partitioning wall 53a into upper and lower chambers. Numeral61 is a first hydraulic cylinder arranged between the first and secondboom members 51, 52 to extend into the upper spacing of the third boommember. The first hydraulic cylinder 61 has a cylinder portion 61aconnected by a pivot 72 to the base portion of the second boom member 52and apiston rod 61b connected by a pivot 71 to the baseportion of thefirst boom member 51 most adjacent to the base portion of the boom.

Numeral 62 is a second hydraulic cylinder having a piston rod 62bconnected to the base portion of the second boom member 52 at a pivot 73and a cylinder portion 62a connected by a pivot 74 to the base portionof the succeeding third boom member 53.

A third hydraulic cylinder 63 is arranged between the third and thefourth boom members 53 and 54, and has a piston rod 63b pivotallyconnected by a pivot 75 to the base portion of the third member 53 and acylinder portion 63a pivotally connected to the top portion of thefourth boom member 54 at 76.

Numeral 77 is a roller carrying the top of the first hydraulic cylinder61, and 78 is a roller carrying the top of the second hydraulic cylinder62.

The arrangement of oil pressure supply lines to the first, second andthird hydraulic cylinders 61, 62 and 63 is as follows. An oil pressuresupply line 79 is connected to a port 80 provided at the base portion ofthe piston rod 61b of said hydraulic cylinder 61 and in communicationwith a compressed oil chamber 61c on an extending side of the firsthydraulic cylinder 61. An oil pressure supply line 81 is connected toaport 82 provided at the base portion of the piston rod 63b of saidthird cylinder 63 and communicating with a compressed oil chamber 63d ona retracting side of the third hydraulic cylinder 63, and a valve 83 forswitching the flow of oil is connected to supply lines 79 and 81. Saidsupply line 81 is connected to the port 82, which moves with the thirdmember 53, depending upon the extention or retraction of the boom, andis formed from a flexible material and retained retractile by anysuitable means.

Said port 80 communicates with chamber 610 through hollow piston rod 61band port 82 communicates with chamber 63d of the retracting side of thethird hydraulic cylinder 63 through a pipe 84. The other chambers 62cand 63c and chambers 61d and 62d of the first, second and thirdhydraulic cylinders 61, 62 and 63 are connected, respectively, tochamber 610 of the extending side of the first cylinder 61, to the line79, and said chamber 63d and to the line 81.

The chamber 610 is connected to chamber 62c through a port 85, a line 86to which a-mechanical check valve 54 is connected, a port 87 and thehollow piston rod 62b, said chamber 62c further being connected to thechamber 63c of the third hydraulic cylinder 63 through a port 88, a line89 to which a mechanical check 58 is connected, a port 90 and the hollowpiston rod 63b. The compressed oil chamber 63d of the third hydrauliccylinder 63 is connected to chamber 62d of second hydraulic cylinder 62through the port 82, a line 91 to which a mechanical check valve C isconnected, and a port 92, said chamber 62d further communicating withchamber 61d of the first hydraulic cylinder 61 through a pipe 93, a port94, and a line 95 to which a mechanical check valve 5D is connected.

The mechanical check valve 5A is secured to the second boom member 52and so positioned that when the first hydraulic cylinder 61 is extendedto its extremity and the second boom member 52 is moved into its utmostextended position, the valve rod 5Ab, normally urged to the closedposition, is forcibly biased by an engaging projection 97 provided onthe internal periphery of the first boom member 51 into opened position.It is automatically returnedto normal, closed position to prevent thesupply of oil to chamber 62c from the first hydraulic cylinder but topermit flow of oil in the opposite direction. The mechanical check valve5B, similarly to the valve 5A, is normally maintained in closed positionto prevent oil pressure supply to chamber 630 of the third hydrauliccylinder 63 and permit flow of oil only in the opposite direction, saidmechanical check valve 5B being forced open when the second hydrauliccylinder 62 and the third boom member 53 reach the utmost extensionstate, because a valve rod SBb of a valve 5Ba normally urged to theclosed position is brought into engagement with a projection 98 providedon the inside wall of the second boom member. At the other position ofthe second hydraulic cylinder 62, valve 5B is mechanically returned toits normal position to check supply to chamber 63c of the thirdhydraulic cylinder 63 and permit flow of oil pressure in the oppositedirection. The mechanical check valve 5C is forcibly opened when thethird hydraulic cylinder 63 namely the fourth boom member 54, reachesits utmost retracted position, because a valve rod 5Cb of a valve 5Canormally kept closed is pushed by the base portion of the fourth member54 of the boom into biased position and, at the other position of thethird hydraulic cylinder 63, mechanically controlled to return to thenormal, closed position to check supply to the compressed oil chamber62d and permit an oil flow in the opposite direction. The mechanicalcheck valve 5D is forcibly opened when the second hydraulic cylinder 62,namely, the third boom member 53 reaches its utmost retracted position,a valve rod 5Db of a valve 5Da normally kept closed is pushed by thebase portion of the third boom member 53 into a biased position. Atother position of the second hydraulic cylinder 62, valve 5D ismechanically returned to its normal position to check oil pressuresupply to the chamber 61d and permit an oil pressure flow in theopposite direction.

In the boom extension means having such piping arrangement as described,if the valve 83 is operated to connect line 79 to the pump line and line81 to the tank, respectively, the first hydraulic cylinder 61 only isextended to move the second boom member 52 into the extended position,since the mechanical check valves 5A and 5B operate to close the lines86, 89. When the first hydraulic cylinder 61, namely, the second member52 reaches its utmost extension, the mechanical check valve 5A is openedby the projection 97, thereby supplying oil to chamber 62c, whereby saidsecond hydraulic cylinder 62 is caused to extend. When said secondhydraulic cylinder 62, namely, the third member 53 reaches the utmostextension, the mechanical check valve 5B is opened by the projection 98and the oil is supplied to the chamber 63c of of the third cylinder 63,this third cylinder 63 is extended to move the fourth boom member 54into its utmost extended position.

Meanwhile, in the chambers 61d, 62d and 63d of cylinders 61, 62 and 63,when said cylinders 61, 62 and 63 are extending, oil is dischargedtherefrom to the tank through the lines 95, 91 and 81 because themechanical check valves 5C and 5D permit the flow in said direction.

When all of the boom members are in their fullest extended positions, ifthe valve 83 is operated to switch the connection of the oil pressuresupply and discharge lines, the third hydraulic cylinder 63 is retractedto move the fourth boom member 54 into the retracted position, since thelines 81 and 85 are kept closed by mechanical check valves 5C and 5D, sothat backpressure is not created in chambers 61d, 62d, due to the loadto be applied thereto. Since, at the utmost retraction of said thirdhydraulic cylinder 63, or the fourth boom member 54, the mechanicalcheck valve 5C is opened by the base portion of the fourth boom member54 and the oil is applied to chamber 62d of the retracting side cylinder62; hence the second hydraulic cylinder 62 is retracted to move thethird boom member 53 into its fully retracted position. When the boommember 53 reaches to the extremity of retraction, the check valve 5D isopened and the oil is supplied to the chamber 61d of the retractingside, so that the first hydraulic cylinder 61 is retracted to cause theretraction of the second boom member 52.

Check valves A, B, C, D and 5A, 5B, 5C, 5D as employed in the first andthird embodiments and valves A, B, C, D as employed in the secondexample may be so adapted as to be indirectly controlled by solenoidsoperating according to the extending and retracting operations ofrespective hydraulic cylinders l1, l2, l3, and 61, 62, 63. The boomextension means according to the present invention is applicable notonly in the boom consisting of four boom members but also in the boomconsisting of any desired numbers of boom members more than three.

The thus constructed extension means of a multistage boom relating tothe present invention has such advantages that the construction andoperation are simplified and the respective hydraulic cylinders areautomatically operated in regular sequence by operating a single valvemeans, thereby to provide the smooth extending and retracting motions ofrespective boom members. v

The boom extension means according to the present invention providesfurther advantages that since the retracting motion of respective boommembers of a multi-stage boom is regulated by controlling the oildischarge and supply from the chambers on the extending sides ofrespective hydraulic cylinders, the chambers on the retracting sidessofrespective hydraulic cylinders become vacuous owing to the loadexertedon boom members, at the time of retraction thereof, hence there is noprobability of disturbing said sequence of retraction of respective boommembers.

What is claimed is:

1. In a boom consisting of at least three telescopically-connected boommembers,

fluid-pressure operated means for extending and contracting said boom,comprising a series of cylinders, the number of which is one less thanthe number of boom members,

a piston reciprocable in each cylinder,

each piston dividing its cylinder into two chambers, one a retractingchamber and the other a chamber for effecting extension, and each pistonhaving a piston rod attached to it at one side,

each cylinder being connected to one of said boom members and eachpiston being connected to the next adjacent boom member,

a first conduit for conducting the motive fluid to and from theextension side of the piston reciprocable in the last cylinder of saidseries,

a second conduit for conducting the motive fluid to and from theretracting side of the piston in the first cylinder in the series,

a reversible valve to which said conduits are connected for reversingthe direction of flow of the motive fluid to said conduits,

a first series of lines connecting the chamber on the retracting side ofeach cylinder with the corresponding chamber in the next adjacentcylinder,

a valve in each said line which is closed, when the boom is retracted,for preventing flow of the motive fluid in one direction through saidline while permitting flow in the opposite direction,

a second series of lines connecting the chamber on the extending side ofeach cylinder with the corresponding chamber in the next adjacentcylinder in the series,

a valve in each of the second series of lines, which is closed, when theboom is extended, for preventing flow of the motive fluid in each lineof said second series in said opposite direction while permitting flowin said one direction,

means actuated when the last cylinder of said series is extended to itsextremity, for opening the valve in the line with which the firstconduit communicates, to connect the chamber in the last cylinder withthe corresponding chamber in the next adjacent cylinder to causeextending movement in said next adjacent chamber, and

means actuated, when the first cylinder in said'series is extended toits extremity, for opening the valve in the line, with which the secondconduit communicates, to connect the extension chamber in the firstcylinder with the corresponding chamber in the next adjacent cylinder tocause extending movement in said next adjacent cylinder, whereby a boomcan extend from the second boom member and successively retract from thelast boom member. i

2. A boom as claimed in claim 1, wherein said first conduit conducts themotive fluid to and from the chamber on the retracting side of the lastcylinder, and said second conduit conducts the motive fluid to and fromthe chamber on the extending side of the first cylinder.

3. A boom as claimed in claim 1, wherein said first conduit conducts themotive fluid to and from the chamber on the extending side of the lastcylinder and said second conduit conducts themotive fluid to and fromthe chamber on the retracting side of the first cylinder. v

4. In a boom comprising at least three telescopicallyconnected boommembers,

fluid-pressure operated means for extending and retracting said boom,comprising a series of hydraulic cylinders disposed between andconnecting adjacent boom members, each of said cylinders including apiston reciprocable in said cylinder, each piston dividing its cylinderinto two chambers, one a chamber for effecting retraction and the othera chamber for effecting extension, and each piston having a piston rodattached to it at one side and extending through the chamber on theretraction side of the cylinder,

a first conduit for conducting the motive fluid to and from the chamberon the extension side of the first hydraulic cylinder in said series,

a second conduit for conducting the motive fluid to and from the chamberon the retraction side of the last hydraulic cylinder in said series,

a reversible valve to which said first and second conduits are connectedfor controlling the direction of flow of the motive fluid through saidfirst and second conduits,

a pipe connecting the chamber on the extension side of each hydrauliccylinder, excepting said last one, with the corresponding chamber in thenext adjacent hydraulic cylinder in the series,

a first valve in said pipe connecting the chamber on the extension sideof each hydraulic cylinder to the corresponding chamber of the nextadjacent hydraulic cylinder, said first valve being adapted to be closedfor preventing flow of the motive fluid from the first hydrauliccylinder side to the last hydraulic cylinder side, and opened forpermitting flow of the motive fluid in either direction through saidpipe, said first valve being normally closed,

a pipe connecting the chamber on the retraction side of each hydrauliccylinder, excepting the last one, with the corresponding chamber in thenext adjacent hydraulic cylinder in the series,

a second valve in said pipe connecting the chamber means actuated toopen the valve in the pipe connecting chambers on the first conduitwhich correspond to extension side, when the hydraulic cylinder of firstcylinder side between the chambers to which the said valve correspondsis extended to its extremity, and

means actuated to open the valve in the pipe connecting chambers on thesecond conduit which corresponds to retraction side, when the hydrauliccylinder of first cylinder side between the chambers to which the saidvalve corresponds is retracted to its extremity;

whereby, the boom can extend from its first member side successively andretract from its last member side likewise.

5.' In a boom comprising at least three telescopicallyconnected boommembers.

fluid-pressure operated means for extending and retracting said boom,comprising a series of hydraulic cylinders disposed between andconnecting adjacent boom members, each of said cylinders including apiston reciprocable in said cylinder, each piston dividing its cylinderinto two chambers, one a chamber for effecting retraction and the othera chamber for effecting extension, and each piston having a piston rodattached to it at one side and extending through the chamber on theretraction side of the cylinder,

a first conduit for conducting the motive fluid to and from the chamberon the retraction side of the first hydraulic cylinder in said series,

a second conduit for conducting the motive fluid to and from the chamberon the retraction side of the first hydraulic cylinder in said series,

a reversible valve to which said first and second conduits are connectedfor controlling the direction of flow of the motive fluid through saidfirst and second conduits,

a pipe connecting the chamber on the extension side of each hydrauliccylinder, excepting said last one, with the corresponding chamber in thenext adjacent hydraulic cylinder in the series,

a first valve in said pipe connecting the chamber on the extension sideof each hydraulic cylinder to the corresponding chamber of the nextadjacent hydraulic cylinder, said first valve being adapted to be closedfor preventing flow of the motive fluid from the first hydrauliccylinder side to the last hydraulic cylinder side, and opened forpermitting flow of the motive fluid in either direction through saidpipe, said first valve being normally closed,

a pipe connecting the chamber on the retraction side of each hydrauliccylinder, excepting the last one, with the corresponding chamber in thenext adjacent hydraulic cylinder in the series,

a second valve in said pipe connecting the chamber on the retractionside of each hydraulic cylinder to the corresponding chamber of the nextadjacent hydraulic cylinder, said second valve being adapted to beclosed for preventing flow of the motive fluid from the last hydrauliccylinder side to the first hydraulic cylinder side, and opened forpermitting flow of said motive fluid in either direction through thelast-named pipe, said second valve being normally closed,

means actuated to open the valve in the pipe connecting chambers on thefirst conduit which corre sponds to retraction side, when the hydrauliccylinder of first cylinder side between the chambers to which the saidvalve corresponds is extended to its extremity, and

means actuated to open the valve in the pipe connecting chambers on thesecond conduit which corresponds to extension side, when the hydrauliccylinder of first cylinder side between the chambers to which the saidvalve corresponds is retracted to its extremity;

whereby, the boom can extend from its first member.

side successively and retract from its last member side likewise.

UNITED STATES PATENT OFFII'JE CER'TIFIQATE 0F (JORRECTION Pat nt No- 3,9 Dated May-7, 197

Inventor(s) Kazuhiro Ohniwa and Seuti Ishikawa It is certified thaterror appears in the above-identified'patent and that said LettersPatent are hereby corrected as shown below:

Co1umn 8,1ine 39, "chambers" should be .--spaces--.

Column 9, line 24, numeral "5 should be --5A.

Column 10, line #7, numeral "81" should be -9l-. column 13, line 20,"first" should be --last---; in

line M3, "retraction" should be ----extension---; and in line 44,"first" should be --last--.

Column 14, line +0, "first" should be --last--.

Signed and sealed this 5th day of November 19 74.

(SEAL) Attest:

McCOY M. GIBSON JRO c. MARSHALL DANN f Attesting Officer Commissioner ofPatents FORM PC4050 uscoMM-oc 60376-Pfl9 U.S GOVERNMENT PRINTING OFFICE:I959 O-JG-33

1. In a boom consisting of at least three telescopicallyconnected boommembers, fluid-pressure operated means for extending and contractingsaid boom, comprising a series of cylinders, the number of which is oneless than the number of boom members, a piston reciprocable in eachcylinder, each piston dividing its cylinder into two chambers, one aretracting chamber and the other a chamber for effecting extension, andeach piston having a piston rod attached to it at one side, eachcylinder being connected to one of said boom members and each pistonbeing connected to the next adjacent boom member, a first conduit forconducting the motive fluid to and from the extension side of the pistonreciprocable in the last cylinder of said series, a second conduit forconducting the motive fluid to and from the retracting side of thepiston in the first cylinder in the series, a reversible valve to whichsaid conduits are connected for reversing the direction of flow of themotive fluid to said conduits, a first series of lines connecting thechamber on the retracting side of each cylinder with the correspondingchamber in the next adjacent cylinder, a valve in each sAid line whichis closed, when the boom is retracted, for preventing flow of the motivefluid in one direction through said line while permitting flow in theopposite direction, a second series of lines connecting the chamber onthe extending side of each cylinder with the corresponding chamber inthe next adjacent cylinder in the series, a valve in each of the secondseries of lines, which is closed, when the boom is extended, forpreventing flow of the motive fluid in each line of said second seriesin said opposite direction while permitting flow in said one direction,means actuated when the last cylinder of said series is extended to itsextremity, for opening the valve in the line with which the firstconduit communicates, to connect the chamber in the last cylinder withthe corresponding chamber in the next adjacent cylinder to causeextending movement in said next adjacent chamber, and means actuated,when the first cylinder in said series is extended to its extremity, foropening the valve in the line, with which the second conduitcommunicates, to connect the extension chamber in the first cylinderwith the corresponding chamber in the next adjacent cylinder to causeextending movement in said next adjacent cylinder, whereby a boom canextend from the second boom member and successively retract from thelast boom member.
 2. A boom as claimed in claim 1, wherein said firstconduit conducts the motive fluid to and from the chamber on theretracting side of the last cylinder, and said second conduit conductsthe motive fluid to and from the chamber on the extending side of thefirst cylinder.
 3. A boom as claimed in claim 1, wherein said firstconduit conducts the motive fluid to and from the chamber on theextending side of the last cylinder and said second conduit conducts themotive fluid to and from the chamber on the retracting side of the firstcylinder.
 4. In a boom comprising at least threetelescopically-connected boom members, fluid-pressure operated means forextending and retracting said boom, comprising a series of hydrauliccylinders disposed between and connecting adjacent boom members, each ofsaid cylinders including a piston reciprocable in said cylinder, eachpiston dividing its cylinder into two chambers, one a chamber foreffecting retraction and the other a chamber for effecting extension,and each piston having a piston rod attached to it at one side andextending through the chamber on the retraction side of the cylinder, afirst conduit for conducting the motive fluid to and from the chamber onthe extension side of the first hydraulic cylinder in said series, asecond conduit for conducting the motive fluid to and from the chamberon the retraction side of the last hydraulic cylinder in said series, areversible valve to which said first and second conduits are connectedfor controlling the direction of flow of the motive fluid through saidfirst and second conduits, a pipe connecting the chamber on theextension side of each hydraulic cylinder, excepting said last one, withthe corresponding chamber in the next adjacent hydraulic cylinder in theseries, a first valve in said pipe connecting the chamber on theextension side of each hydraulic cylinder to the corresponding chamberof the next adjacent hydraulic cylinder, said first valve being adaptedto be closed for preventing flow of the motive fluid from the firsthydraulic cylinder side to the last hydraulic cylinder side, and openedfor permitting flow of the motive fluid in either direction through saidpipe, said first valve being normally closed, a pipe connecting thechamber on the retraction side of each hydraulic cylinder, excepting thelast one, with the corresponding chamber in the next adjacent hydrauliccylinder in the series, a second valve in said pipe connecting thechamber on the retraction side of each hydraulic cylinder to thecorresponding chamber of the next adjacent hydraulic cylinder, saidseconD valve being adapted to be closed for preventing flow of themotive fluid from the last hydraulic cylinder side to the firsthydraulic side, and opened for permitting flow of said motive fluid ineither direction through the last-named pipe, said second valve beingnormally closed, means actuated to open the valve in the pipe connectingchambers on the first conduit which correspond to extension side, whenthe hydraulic cylinder of first cylinder side between the chambers towhich the said valve corresponds is extended to its extremity, and meansactuated to open the valve in the pipe connecting chambers on the secondconduit which corresponds to retraction side, when the hydrauliccylinder of first cylinder side between the chambers to which the saidvalve corresponds is retracted to its extremity; whereby, the boom canextend from its first member side successively and retract from its lastmember side likewise.
 5. In a boom comprising at least threetelescopically-connected boom members. fluid-pressure operated means forextending and retracting said boom, comprising a series of hydrauliccylinders disposed between and connecting adjacent boom members, each ofsaid cylinders including a piston reciprocable in said cylinder, eachpiston dividing its cylinder into two chambers, one a chamber foreffecting retraction and the other a chamber for effecting extension,and each piston having a piston rod attached to it at one side andextending through the chamber on the retraction side of the cylinder, afirst conduit for conducting the motive fluid to and from the chamber onthe retraction side of the first hydraulic cylinder in said series, asecond conduit for conducting the motive fluid to and from the chamberon the retraction side of the first hydraulic cylinder in said series, areversible valve to which said first and second conduits are connectedfor controlling the direction of flow of the motive fluid through saidfirst and second conduits, a pipe connecting the chamber on theextension side of each hydraulic cylinder, excepting said last one, withthe corresponding chamber in the next adjacent hydraulic cylinder in theseries, a first valve in said pipe connecting the chamber on theextension side of each hydraulic cylinder to the corresponding chamberof the next adjacent hydraulic cylinder, said first valve being adaptedto be closed for preventing flow of the motive fluid from the firsthydraulic cylinder side to the last hydraulic cylinder side, and openedfor permitting flow of the motive fluid in either direction through saidpipe, said first valve being normally closed, a pipe connecting thechamber on the retraction side of each hydraulic cylinder, excepting thelast one, with the corresponding chamber in the next adjacent hydrauliccylinder in the series, a second valve in said pipe connecting thechamber on the retraction side of each hydraulic cylinder to thecorresponding chamber of the next adjacent hydraulic cylinder, saidsecond valve being adapted to be closed for preventing flow of themotive fluid from the last hydraulic cylinder side to the firsthydraulic cylinder side, and opened for permitting flow of said motivefluid in either direction through the last-named pipe, said second valvebeing normally closed, means actuated to open the valve in the pipeconnecting chambers on the first conduit which corresponds to retractionside, when the hydraulic cylinder of first cylinder side between thechambers to which the said valve corresponds is extended to itsextremity, and means actuated to open the valve in the pipe connectingchambers on the second conduit which corresponds to extension side, whenthe hydraulic cylinder of first cylinder side between the chambers towhich the said valve corresponds is retracted to its extremity; whereby,the boom can extend from its first member side successively and retractfrom its last member side likewise.